RKI Instruments Gas Tracer User Manual
Page 15
Gas Tracer Operator’s Manual
Instrument Description • 7
Combustible Gas Sensors
% LEL Sensor (NC-6264A)
The % LEL sensor detects combustible gas in the % LEL range. It uses
a catalytic element for detection. The reaction of gas with oxygen on
the catalyst causes a change in the resistance of the element which
affects the current flowing through it. The current is amplified by the
Gas Tracer’s circuitry, converted to a measurement of combustible gas
concentration, and displayed on the LCD.
PPM Sensor (SH-8641)
The ppm combustible sensor detects combustible gas in the ppm
range. It is used in Leak Check Mode. It is a combination catalytic/
MOS type sensor with a current output. The current is amplified by
the Gas Tracer’s circuitry, converted to a measurement of combustible
gas concentration, and displayed on the LCD.
%Volume Sensor (TE-7561)
The % volume sensor detects combustible gas in the % volume range.
It uses a thermal conductivity (TC) element for detection. The
presence of combustible gas cools the element causing a change in the
resistance of the element which affects the current flowing through it.
The current is amplified by the Gas Tracer’s circuitry, converted to a
measurement of combustible gas concentration, and displayed on the
LCD.
Oxygen Sensor
The O
2
sensor is a galvanic type of sensor. A membrane covers the cell
and allows gas to diffuse into the cell at a rate proportional to the
partial pressure of oxygen. The oxygen reacts in the cell and produces
a voltage proportional to the concentration of oxygen. The voltage is
measured by the Gas Tracer’s circuitry, converted to a measurement
of gas concentration, and displayed on the LCD.
CO Sensor
The CO sensor is an electrochemical cell that consist of two precious
metal electrodes in a dilute acid electrolyte. A gas permeable
membrane covers the sensor face and allows gas to diffuse into the
electrolyte. The gas reacts in the sensor and produces a current
proportional to the concentration of the target gas. The current is
amplified by the Gas Tracer’s circuitry, converted to a measurement of
gas concentration, and displayed on the LCD.